1. Field of the Invention
The present invention relates generally to a scroll compressor of the type comprised of a casing including a compressor mechanism portion for compressing a gas therein, and more particularly to an anti-rotation mechanism for a scroll compressor, the overall size of which can be reduced, thereby enabling miniaturization of the scroll compressor.
2. Description of the Related Art
Such a scroll compressor comprises a fixed scroll member and an orbiting scroll member each including an end plate on which a spiral-shaped wrap is provided in an upright position. These scroll members are assembled in a superimposed manner with these wraps engaged with each other to allow the orbiting scroll member to orbit with respect to the fixed scroll member without rotating about its axis. The end plate of the fixed scroll member has a discharge port at its center and a suction port in its outer periphery, and a gas is drawn by suction through the suction port. Then the closed space defined by these scroll members is moved toward the center of the orbiting movement to reduce the volume of the closed space, thereby compressing the sucked gas. The thus-compressed gas is discharged through the discharge port.
As disclosed in, for example, U.S. Pat. No. 4,396,364, in such a scroll compressor, an anti-rotation mechanism for preventing the orbiting scroll member from rotating about its axis is interposed between a back surface of the orbiting scroll member opposite to its wrap and the surface of the frame facing the back surface.
A primary disadvantage of the prior anti-rotation mechanism is that no consideration is given to a reduction in the overall size of the compressor. Specifically, in order to seal a back pressure or bear a thrust force which acts upon the orbiting scroll member, the end plate of the orbiting scroll member is provided with an extension which does not influence the compression function of the compressor. As a result, the overall diametral size of the compressor must correspondingly be increased.